In vitro systems are being used to study the mechanism of action of gastrin, secretin, cholecystokinin and vasoactive intestinal peptide hormone with their specific membrane receptors. Clinical investigations are directed toward developing alternative forms of therapy for and elucidating the pathogenesis of disorders characterized by ectopic production of gastrointestinal hormones (e.g. Zollinger-Ellison syndrome and pancreatic cholera). BIBLIOGRAPHIC REFERENCES: Garnder, J. D., Christophe, J., Robberecht, P., and Conlon, T. P.: Membrane receptors for VIP and secretin in pancreatic acinar cells. In Hormonal Receptors in Digestive Tract Physiology. (S. Bonfils, P. Fromageot, G. Rosselin, eds.) Elsevier/North-Holland Biomedical Press, North Holland 1977, pp. 227-235. Gardner, J. D., Long, B. W., Uhlemann, E. R., and Peikin, S. R.: Membrane receptors for VIP and secretin. Proceedings of the International Symposium on Gut Hormones - Lausanne - 18/19th June 1977 (In Press).